NASA and the European Space Agency are planning to launch three spacecraft into orbit around the sun, three million miles apart, and have them fire lasers at each other to prove the theory of general relativity.

The lasers will be used to measure tiny changes in distance between the spacecraft — actually, between floating cubes of gold platinum within each spacecraft — hoping that those changes will prove the existence of gravitational waves, the last remaining piece of Albert Einstein's theory of general relativity yet to be proven. According to Glasgow University's Prof. Jim Hough, a member of the team that planned this experiment:

"[Gravitational waves] are produced when massive objects like black holes or collapsed stars accelerate through space, perhaps because they being pulled towards another object with greater gravitational pull like a massive black hole.... Unfortunately we haven't been able to detect them yet because they are very weak. However, the new experiments we are working on have great potential to allow detection."

The team hopes that by being able to detect gravitational waves, they'll be able to use those ripples in space-time to gather new information about the universe that can't be collected using light, x-rays, or radio waves.